Diisocyanate polyaddition products dispersed in polyethers or polyesters are already known. According to German Auslegeschrift No. 1,168,075, diisocyanates are reacted with bifunctional primary alcohols in a polyether or polyester having a molecular weight of 500 to 3,000 as dispersing medium, the polyether or polyester containing at least two, exclusively secondary, hydroxyl groups in the molecule. According to German Auslegeschrift No. 1,260,142, polyaddition of compounds containing isocyanate groups and NH groups is carried out in situ in a polypropylene glycol ether used as dispersing medium. The processes give rise to dispersions of polyurethanes, polyureas or polyhydrozodicarbonamides in polyvalent higher molecular weight compounds which have hydroxyl groups. They are recommended as thickeners for textile or dye auxiliaries because of their viscosities, which are high even at low solid contents. A 10% (20%) polyhydrazodicarbonamide dispersion in a polypropylene glycol ether according to German Auslegeschrift No. 1,260,142, for example, has a viscosity of over 10,000 cP (200,000 cP) at 25.degree. C. This is more than 10 (200) times the viscosity of the pure dispersing agent. When attempts are made to prepare a 40% dispersion, the reaction mixture solidifies before polyaddition has been completed. The high viscosities obtained at even relatively low solids contents severely limit the possibilities of using the products of the process because, in many fields of application, it is not possible to dose these products with the aid of the usual dosing devices. Thus, for example, when producing polyurethane foams, for which such dispersions could be used according to German Offenlegungsschrift No. 2,423,984, the viscosities to the starting materials should be below 2500 cP if they are to be processed in the high pressure machines normally employed.
According to German Offenlegungsschrift Nos. 2,513,815; 2,550,833 and 2,550,862, substantially anhydrous, relatively low viscosity dispersions of polyureas and/or polyhydrazodicarbonamides in higher molecular weight and optionally also lower molecular weight compounds containing hydroxyl groups can be obtained by carrying out the polyaddition reaction continuously in continuous flow mixers. This process has the disadvantage of requiring a relatively complicated and expensive dosing and mixing technique. Moreover in some cases, when the solid concentrations are relatively high, removal of the heat of reaction may be difficult.
According to the two earlier proposals by the present applicants in German Offenlegungsschriften Nos. 2,550,796 and 2,550,797 stable dispersions of polyisocyanate polyaddition products in hydroxyl containing compounds as dispersing agents are obtained by in situ reaction of polyisocyanates with aminofunctional compounds in dispersing agents, if the reaction is carried out in the presence of water. The starting compounds used for this reaction may contain ionic groups. It was surprisingly found that stable dispersions having the required low viscosity could be produced even in simple stirrer apparatus, particularly if the reaction mixture contained about 7 to 35% by weight of water, based on the total quantity of reaction mixture including water. This is particularly surprising in view of the fact that a water content of, for example, 10, 15 or 20% by weight is known to increase the viscosity of a polyalkyleneether glycol at 25.degree. C. to 4,8 or over 50 times the original viscosity. If the water content is increased even further, the solution or emulsion initially obtained in many cases separates out into its different phases. Both the high increase in viscosity and the phase separation would inevitably lead a routineer in the art to expect that the addition of water would be unsuitable for the industrial production of low viscosity polyisocyanate polyaddition products in hydroxyl containing compounds, particularly since water would be an additional reactant which could interfere with the isocyanate polyaddition reaction.
During further development of the process according to the above mentioned German Offenlegungsschrift, it has now been found that the physical properties of polyurethane resins produced from the dispersions could be further improved or modified if reaction of substances capable of forming aminoplast and/or phenoplast condensates is carried out either side by side with the polyisocyanate polyaddition reaction or subsequently in the hydroxyl containing dispersing agent. The process according to German Offenlegungsschriften Nos. 2,550,796 and 2,550,797 is preferably employed, that is to say the polyisocyanate polyaddition reaction is carried out in the presence of more than 4% by weight, preferably 7 to 35% by weight, most preferably 10 to 25% of water, based on the quantity of reaction mixture including water.
A process for the preparation of dispersions of aminoplast condensates in organic polyhydroxyl compounds has already been disclosed in German Offenlegungsschrift No. 2,324,134. In this process, the known method of preparation of aminoplast condensates by oligocondensation or polycondensation of compounds capable of aminoplast formation is carried out in situ in the organic polyhydroxyl compounds used as reaction medium. According to a further development of this process described in an earlier proposal by the present Applicants in German Offenlegungsschrift No. 2,512,385, the resulting dispersions of polycondensates in hydroxyl containing compounds are after-treated at temperatures of between -5.degree. C. and 180.degree. C. with aliphatic or cycloaliphatic monoamines or polyamines which have at least one primary or secondary amino group and are gaseous or liquid at room temperature or with alkyl hydrazines which have at least one primary or secondary amino group and are gaseous or liquid at room temperature.